Mix equal parts oil and vinegar - about 1/8 cup of each to start and increase depending on how many you are making. Mix cheese and vinegar mixture until cheese is lightly coated.

Assemble watermelon, cheese, small folded pieces of prosciutto and mint leaves on a toothpick, starting with the watermelon and cheese on the bottom, topped by the prosciutto and finally the mint leaf. Serve at once.